So I store my wallet.dat files offline in a truecrypt file. When I want to send BTC I shutdown the bitcoin.exe app and swap out the wallet.dat file. And then run a -rescan to load up the updated wallet.dat file.

This process has been working fine for some time now. But now all of a sudden, I can't get the client to accept any of my stored wallet.dat files without giving an error and crashing.